1. Field of the Invention
The present invention relates to an alumina sintered body having an electrode embedded therein, such as a heater, an electrostatic chuck, and a susceptor for high frequency application, which are used in a semiconductor manufacturing device such as a CVD device and an etching device.
2. Description of the Related Art
In a conventional semiconductor manufacturing process, an alumina member, such as an electrostatic chuck having an electrode embedded in an alumina sintered body and a heating device having a resistance heating element embedded in an alumina sintered body is used. As disclosed in Japanese Patent Application Laid-open No. H11-12053, there is a known device in which a metal terminal is further embedded in contact with a metal electrode in a ceramic substrate on the back surface side opposite to the surface on which a wafer is to be mounted and a power-supply connector is connected to the metal terminal to supply the power to the metal electrode.
However, particularly in the case of a Coulomb-type electrostatic chuck using an alumina sintered body, the thickness of a dielectric layer is generally as thin as 0.4 mm or less, and it can lower the strength thereof. As the thickness decreases, cracks can be generated in the alumina substrate between the wafer mounting surface and the metal electrode when the alumina substrate is integrally sintered with the metal electrode and the metal terminal, since a thermal expansion coefficient differs between alumina and a metal. As the distance from the wafer mounting surface to the metal electrode decreases, the strength of the corresponding alumina substrate decreases, and a crack generation rate increases accordingly. A product having cracks becomes a defective product, and its yield is decreased.